One of these...
http://www2.towerhobbies.com/cgi-bin...?&I=LXGGG7&P=7
your finger, a wet rag and a scrap of balsa now and then to get the excess.
You can keep the glue from setting up in the applicator by wrapping the tip with plastic warp. An clear it with a T-pin if it clogs.
You don't need pressure just make sure the two surfaces have good contact. I wait about a half hour or an hour for it to setup....there's always other stuff to do.